Currently, transmission of torque between parallel drive shafts and driven shafts positioned at a distance of up to several meters from each other is achieved by means of a transmission shaft, which typically is installed perpendicularly to the shafts and connected to each shaft through angular gearboxes. The fact that in such configuration the torque changes direction twice decreases the efficiency coefficient of the device, especially if gears of the angular gearboxes are of a hypoid type, for which the teeth of the gears roll with slippage. The method, popular in the design of steam locomotives, is never used in modern vehicles.
The drive wheel of a locomotive, powered by a connecting rod from the piston of the steam engine, is connected by a coupling rod to the other wheel and by these means sends torque to a parallel shaft.
One of the reasons why the transfer of torque by connecting rods fails in modern vehicles is the weight of the connecting rods, which grows proportionally to the distance between the shafts. Moreover, the use of connecting rods leads to creation of unbalanced forces which vary in strength and direction, thus requiring the use of counterweights that significantly increase the overall weight of the vehicle. This becomes apparent from the study of locomotive drive wheels design, where one side of the side of connecting rod is connected to wheel axle (that connected to the rim of the wheel by spokes), and another side of the rod is coupled to the cast disk.
The U.S. Pat. No. 2,203,975 by Young describes a device where, in order to balance the torque for two drive wheel pairs, the axles are implemented as crankshafts with three cranks offset by 120 degrees, while the cranks connected by connecting rods. Such placement of cranks every 120 degrees allows consistent transmission of torque. However, for such configuration, the transmission of torque by one or two connecting rods creates particular moments with a zero torque, which is undesirable. The crankshafts described by Young can be replaced by eccentrics with an equal to the crankshaft eccentricity, or being used in combination if needed. Thus, in MPK F16C 3/04 one can find a description of crankshafts, shafts with eccentrics, cranks, eccentrics with some of their characteristics being functionality grouped together. Hereinafter, for simplicity we assume that functionality of eccentrics is applicable to cranks (crankshafts) and vice versa.
Presently, the mentioned connecting rods used in industry experience alternating forces during its operation. They are manufactured from steel alloys with a specific strength up to 100 kg/mm2, which is close to the maximum strength for such material. It should be noted that there are materials, such as steel cable wires on the market, specifically designed to operate in tension, with a specific strength of 200 kg/mm2.
The use of flexible eccentric sectors secured on the driving and driven shafts for the torque transfer has been disclosed in U.S. Pat. No. 4,753,628 by Gore, where each sector on the driving shaft and the corresponding sector on the driven shaft are connected by a circular cable. Such device has following disadvantages:
i) Each cable become tense at the moment when the torque is transferred, however, the same cable becomes loose when the torque is transferred by other cables. When this cable resumes the torque transfer, the driving segment is (slightly) displaced against the driven segment and after a number of cycles such accumulated displacement will impair the functionality of the device.
ii) Each circular cable in the set is slightly differs from other, which further increases the rate of accumulating the mentioned displacement (driving segments against the corresponded driven ones).
iii) Such structure (disclosed by Gore) requires a synchronized rotation of the driving and driven shafts. The synchronization with a V-belt suggested by the author will extend the time of torque transmission only insignificantly since it is based on a friction behavior of the belt. It is well-known that V-belts transmit force with a slight slippage making the angular offset of the driving shaft against the driven shaft inevitable. The alternative synchronization option proposed by the author of the present invention implies using a whole eccentric having a two self-tightening cable turns. Such option is also based on the frictional properties of the synthetic cable, which are not sufficient for precise operation. Accordingly, a gear belt or a chain is required to ensure continuous synchronization. Application of a complete eccentric without a bearing, as acknowledged by Gore will lead to a loss of the transferred torque due to the cable friction against the eccentric.
iv) The use of a gear belt or a chain for synchronization purposes is not suggested or recommended since it would lead to cable straining and sliding at the beginning of each force transmission cycle, leading to its wearing and failure.
The proposed invention overcomes above mentioned drawbacks by transferring the torque between respective eccentrics by cable through rotating or friction type bearings. Another important difference is that the three eccentrics (or cranks) that transmit force to the cables via the bearings automatically synchronize the rotation of the driving and driven shafts.
The current invention overcomes the mentioned negative aspects of using connecting rods.